What you need to know

What you need in order to measure

What are Smart Devices?

A smart device is an electronic gadget that is able to connect, share and interact with its user and other smart devices. Although usually small in size, smart devices typically have significant computing power.

We are concerned with testing only with those smart devices that have built-in loudspeakers or microphones.

These could be smart speakers, mobile devices, tablets, intercoms, and security cameras.

The example we will test is the Amazon Echo Dot.

VIDEO: How to test a smart device

Let’s see how this works in practice. The Device Under Test (DUT) in this video is an Amazon Echo Dot. The concepts discussed also apply to other types of Smart Devices.

The Open Loop challenge

Smart Devices have to be tested using an "Open Loop" rather than a "Closed Loop" test. Conceptually, open loop tests can be slightly more challenging because the test procedures have a couple of steps more than in closed loop tests. Also, not all commercially-available analyzers are capable of testing open loops.

Fortunately, the NTi Audio Smart Device Testing solution ensures that open loop testing is not a challenge at all.

For your interest and understanding, we now discuss the difference between open and closed loop testing:

A Closed Loop Loudspeaker Test

A loudspeaker test is defined as being "closed" when the generator is connected directly to the loudspeaker under test. Therefore, in a Closed Loop loudspeaker test, we connect the sound generator directly to the wires at the back of the loudspeaker under test and play the test signal. The response of the loudspeaker to this test signal is measured with a measurement microphone, and recorded by the analyzer.

A Closed Loop Microphone Test

Similarly in a Closed Loop microphone test, the analyzer is connected directly to the wires on the back of the microphone under test. We play the test signal through a calibrated loudspeaker, and the response of the microphone is recorded by the analyzer.

An Open Loop Loudspeaker Test

For a loudspeaker test on the Amazon Echo, we have no direct physical access to the back of the loudspeaker in the Echo itself (without destroying the Echo). The test signal is fetched by Alexa from the Amazon Cloud. As the generator is thus not connected directly to the loudspeaker under test, we have what is considered to be an Open Loop loudspeaker test.

An Open Loop Microphone Test

To test the microphone array in the Amazon Echo, we also have no direct physical access to the back of the microphones in the Echo itself (again without destroying the Echo). The signal recorded by the Echo microphones is stored on the Amazon Cloud and played back manually to the Analyzer. As the analyzer is not connected directly to the microphones under test, we have what is considered to be an Open Loop microphone test.